could be a geranium that mother nature has produced. Do you have geranium in your garden?
I grew purple haze a few years ago and I am getting all sorts of flower colours from its seeds.

Thanks Eileen, yes, I have several, from deep pink (Ann Folkard I think) to a common pale pink, and a pale blue in the front garden …

Of the few I have I find the white one is much more vigorous than the others.
I'd be tempted to split the blue ones from the white and try to grow the on away from them onesto give them a better chance of spreading.